Nanostructured Hyperbolic Metamaterials for Magnetoplasmonic Sensors

Abstract

We demonstrate numerically a concept for highly integrated magnetoplasmonic biosensors made with nanostructured magnetooptical (MO) hyperbolic metamaterials (HMMs). The concept is based on the use of enhanced amplitudes of ultranarrow peaks of the transverse magnetooptical Kerr effect (TMOKE). In contrast to conventional magnetoplasmonic transducers that employ wide surface plasmon resonances, we use bulk plasmon polariton modes in HMMs. In sensing through changes in the refractive index of water, a figure of merit on the order of 8 × 102 was observed, to be compared with 590 for non-MO HMMs. This allows for improved resolution detection of low-molecular-weight analytes at concentrations on the order of picomolar.

Design of Nanoarchitectures for Magnetoplasmonic Biosensing with Near-Zero-Transmittance Conditions

“…To illustrate applications in biosensing, we consider the refractive index of the analyte region varying in the range 1.3 ≤ n a ≤ 1.5, which may represent an aqueous medium with increasing concentration of the target sample. 2 Moreover, the suitability of this was found constant and as large as S(λ) = 118 nm/RIU, which is comparable to previous proposals 46 but surpassing limitations associated with the rapid decay of TMOKE when increasing the analyte refractive index. In eq 5, Δλ res is the wavelength shift of the maximum TMOKE peak due to the change Δn a in the refractive index of the analyte medium.…”

“…An important parameter to measure the resolution of a sensor is the FoM, defined as FoM = S/Γ, which relates the sensitivity to the line width (Γ) of the TMOKE curve (for each n a ). Since TMOKE exhibits a Fano-like shape, Γ can be obtained by fitting numerical results in Figure 6a with functions 46 A B r TMOKE ( /2 )…”

New Horizons in Near-Zero Refractive Index Photonics and Hyperbolic Metamaterials

“…150 Attempts to surpass these drawbacks include HMMs interfaced with chiral metasurfaces, 151 new concepts for manufacturing hyperbolic, 116,152,153 and ENZ metamaterials, 154 as well as the fabrication of magneto-optical (MO) and/or magnetically-active HMMs. 118,155−159 In MO-HMMs one can take advantage of the transverse MO Kerr effect (TMOKE), with sharp Fano-like curves, to enhance the resolution levels of HMM-based biosensors, 149 following a similar approach previously introduced using magnetic nanostructures. 160−166 To illustrate the last mechanism, we consider the grating coupled MO-HMM in Figure 4e, composed by alternating layers of dielectric MO material (BIG in this case) and Ag.…”

“…(f) Fano-like TMOKE curves for the magnetoplasmonic structure in (e) when varying the superstrate refractive index from 1.333 to 1.337. Reproduced with permission from ref . Copyright 2022 ACS.…”

“…In addition, biodetection is limited to achiral analytes, making it necessary to use fluorescence-enhanced biosensing techniques for the detection of chiral biomolecules . Attempts to surpass these drawbacks include HMMs interfaced with chiral metasurfaces, new concepts for manufacturing hyperbolic, ,, and ENZ metamaterials, as well as the fabrication of magneto-optical (MO) and/or magnetically-active HMMs. ,− In MO-HMMs one can take advantage of the transverse MO Kerr effect (TMOKE), with sharp Fano-like curves, to enhance the resolution levels of HMM-based biosensors, following a similar approach previously introduced using magnetic nanostructures. − To illustrate the last mechanism, we consider the grating coupled MO-HMM in Figure e, composed by alternating layers of dielectric MO material (BIG in this case) and Ag. Instead of using the reflectance curves (as in conventional non-MO HMM), we may use the TMOKE (as seen from Figure f) to reach FOM values as high as 840.…”